Spark plug



L. M K. FIELD Dec. 28, 1954 SPARK PLUG Filed Aug. 31. 1951 LLOYD- McKmsav FIELD %?P flTTORNEY SPARK PLUG Lloyd McKinsey Field, New London, Ohio; Floyde Josephine Field Karcher, executrix of said Lloyd McKinsey Field, deceased, assignor, by mesne assignments, to Andrew R. Cochrane, trustee, Pittsburgh, Pa.

Application August 31, 1951, Serial No. 244,506

2 Claims. (Cl. 123-169) This invention relates to an improved spark plug of the general type in which an electrode-valve controlled passage admits fiuid into an engine. cylinder, in which said plug is installed, on the induction stroke of the piston.

The plug includes an insulator having a longitudinal center bore with a valve seat at its inner. terminus within a recessed valve-head enclosure section, compression abutment means and upper shoulders for the compression ring between which said insulator is secured within the metal shell and is sealed against gas compression loss from between the insulator and wall of the metal shell.

Compressed gas loss through the insulator center bore is prevented by the electrode-valve head being driven to seat at the terminus of the insulator center bore with the full power of the compression stroke of the piston within the cylinder in which the plug is installed. Said electrodevalve being released on the induction stroke, it will seat on its inner surface within the insulator recessed chamber on the metal seat of the lower bore of the shell through which bore the extended portion of said electrode-valve will be held suspended until the following engine compression stroke lifts and drives it back into said insulator seat in perfect center alignment extending through the shell bore presenting its extended terminus in exact predetermined gapping distance from the ground electrode which extends from the shell. The insulator bore sealed by the electrode-valve head and said valve head in this firing position, enclosed within the insulator recessed section is further removed from its lower metal seat on the shell than the electrodes gapping distance. Positioned thus the valve extended section is centered for its length by compressed gas equal distance at all points from inner metal walls of the lower bore of the shell through which the extended electrode valve passes. This arrangement therefor removes the necessity for the insulation of the thin porcelain walls extending down into this inner reduced bore of the metal shell as this improved design permits an arrest seat for the valve head on the metal shell, resulting in a material reduction in cost.

A further object, of interest to the engine manufacturer, will be the possible reduction of the size of the hotspots in the engine head for spark plug ports, since in this structure the threaded lower section of spark plug shells may be greatly reduced in overall diameter.

Another object is the greatly increased life at reduced cost to the useri for it is a well known fact that the best of insulators will not infreouentlv burn off at their tip end because their thin wall is held in direct intense heat. Very little of the insulator in this design meets direct heat and then only in the heavv part. This leaves only the electrode in direct heat and because of the alloy of which it is made it will give a creditable life at very low cost and it is readily replaceable.

With the above and other objects becoming apparent as the invention is better understood, the same consists of the novel form, combination and arrangement hereinafter more fully described, shown in the accompanying drawing, and claimed.

In the drawing:

Figure 1 is a longitudinal sectional view of a spark plug embodying the improvements.

Figure 1a is a partial longitudinal sectional view of another form of spark plug.

Figure 2 is a lower end view of the insulator.

Figure 3 is an upper end view of the valve head arresting seat within the steel shell.

In the drawing, a construction is shown adapted to 2 a attainment of the desired ends, and while this construc tion is" rather specifically described, it is to be understood thatvariations may be made within the scope of the invention.

Asillustrated, the spark plug includes a metallic shell 5 that has a reduced lower end 6 externally threaded as 6 for internal combustion engine. The annular wall portion 7 of the shell above the reduced lower end 6 hasa relatively large chamber 8, while the reduced lower end of the shell has a chamber 9 of lesser diameter than the chamberS and the chamber 9 is in communication with a reduced axial passage 10 through the reduced end. As

illustrated in Figure 1, there is shown an upwardly tapering seat 11 at the juncture 9 and the reduced lower end 6 of the shell below the chamber 9 is of increased thickness to provide an upward ly facing shoulder or seat.12'. Asealing ring 13 of the usual type is threaded into the upper end of the shell 5; A ground electrode 14 is carried by the lower reduced end of the shell.

An insulator 15 is mounted in the shell 5 and has an en larged annular portion 15 substantially filling the chamher 8, suchenlarged portion defining a downwardly facing shoulder 17 in spaced relation to the tapering seat 11 of the shell with a gasket 18 interposed between said shoulders. The insulator 15 has a bore 16 extending completely therethrough, and the lower end of the bore within the chamber 9 at the lower end of the shell forms a valve seat 25.

A free floating positive electrode comprising a disklike head 19 is disposed in the chamber 9 of the shell and has an upwardly projecting conical portion constituting a valve for engaging and closing the seat 25 at the lower end of the insulator bore 16.

A depending stem 21 is carried by the electrode head 19 and extends downwardly through the bore 10 at the lower reduced end of the shell for sparking association with the negative electrode 14. The diameter of the electrode head 19 is greater than the diameter of the bore 10 so that upon a suction stroke in an internal combustion engine, the marginal portion of the positive electrode head 19 will be supported on the shoulder 12 for retaining the free floating positive electrode element in the spark plug assembly. As shown in Figure 3, the upper face of the shoulder 12 is diametrically grooved at 22 so that when the electrode head 19 is seated on the shoulder 12, fluid drawn in through the insulator bore 16 may flow therethrough and by way of the bore 10 to the engine cylinder. A tubular terminal post 24 is mounted in the upper end of the insulator 15 and a sinuous metal strip conductor 26 forms a current connection between the post 24 and the positive electrode head 19, the lower end of the conductor 26 being suitably engaged with the positive electrode element.

As shown in Figure 1a, the insulator 15 at the lower end of the bore 16 has a well defined conical seat 25 that is engaged by the conical head 19 of the free floating positive electrode. In this form of the invention the conductor 26 that extends downwardly from the post 24 is embedded in the upper end of the conical head 19 as at 16.

From the above detailed description of the invention, it is believed that the construction and use of the spark plug will at once be apparent, it being noted that the tubular terminal post 24 and bore in the insulator 15 permits induction of fluid to the engine cylinder upon a suction stroke and at which time the free floating positive electrode element will be moved away from its seat at the lower end of the insulator and with such fluid flowing through the grooves 22 between the positive electrode and the shoulder 12 of the shell. On the following compression stroke the positive electrode element is forced upwardly through the chamber 9 and into engagement with the seat at the lower end of the insulator to seal 01f the bore 16 and the passage through the terminal post, and when so disposed the lower stem end 21 of the electrode is in proper sparking relation to the negative electrode 14. It will be observed that the free floating positive electrode element 19 finds support on a shoulder at the lower end of the spark plug Patented Dec. 28, 1954 mounting in a spark plug port at thehead of an of the two chambers 8 and shell'upon' a suction'stroke of the engine and the only time this positive electrode/element is engaged with the insulator is on the compression stroke.

I claim:

1. Aspank gplujgi comprisinga shell having an zexternalsw ly' threaded reduced lowers-end, ta groundtelectrode can ried :zby: theneduced end,: an upwardly facing-, annular shoulder at the terminus of the lower end defining -a restrieted cylindrical-passage-through the lower endqanda chamber in; the; ,-lower vend above the shoulder, said shouldermbeing .relativelywide and flat; and in a plane,v

normal-4o thelongitudinal axis; of the shell, an insulator witha ;,longit udinal 1 here therethrough mounted s in the shell: and having a reduced; lower end extending into said v chamberg, a;tubula r terminal post atithe upper end ofv trode hav thro h ade.

2. Aspark: plugcomprising.a: shellhaving an externally threaded ,reduced lower end, a :ground electrode carried by the reduced-end, an insulator with a longitudi-r;

ml bore therethrough mounted in the shell, a tubular terminalpostnat the upper .endof the boresin ,theVin-W sulator, an upwardly facing annular shoulder on the shell below the lower end ofwthe insulator defining a restricted cylindrical passage through the lower end of the shell, said shoulder being relatively wide and flat and in a plane normal to the longitudinal axis of the shell, a free-floating positive electrode in the. shell having a head with a relatively flat bottomface -and a conical valve at itsauppen, side adapted selectively to reston said shoulder inthe shelland seatinand seal .the lower end of nthe bore inthe insulator, a sterndepending from the electrode head for cooperation .withthe. groundelectrode and a current conductor strip in the insulator bore connecting the; terminalpost'and positive electrode.

References Cited-in the file of this;Patent UNITED STATES PATENTS 

